This proposal seeks to extend our study of nonselective cation channels and calcium-activated chloride channels in airway smooth muscle cells. Experiments will determine the degree to which these channels are activated by inflammatory mediators associated with asthma, and the processes linking receptor binding and channel activation. Numerous spasmogens are released in asthma and the diversity of mediators produced during airway inflammation suggests that the identification of common excitation/contraction coupling pathways may lead to effective strategies to limit bronchospasm. The degree to which inflammatory compounds, known to be released during asthmatic bronchoconstriction, activate non-selective cation channels and calcium-activated chloride channels in airway smooth muscle is currently unknown. Our recent studies have identified mechanisms by which acetylcholine activates ICat and ICI(Ca). The current reapplication seeks to extend these studies on the molecular processes linking receptor coupling to channel activation, and to gain clinically relevant information about the link between persistent airway inflammation and the activation of these ion channels. Our central hypothesis is that nonselective cation channels and calcium release channels are activated by inflammatory mediators, and that this activation results in a sustained increased in the calcium permeability and sustained depolarization of the myocyte. We proposed to determine the extent to which inflammatory substances activate these channels in airway smooth muscle cells, determine the post-receptor mechanisms associated with receptor/channel coupling, and determine the role of specific calcium release processes in channel activation, including the role of quantal calcium release events (calcium sparks) in the activation of ICI(Ca) channels.